Problem: Simplify the following expression: $q = \dfrac{7p}{10} + \dfrac{4p}{9}$
Explanation: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $10$ and $9$ $\lcm(10, 9) = 90$ $ q = \dfrac{9}{9} \cdot \dfrac{7p}{10} + \dfrac{10}{10} \cdot \dfrac{4p}{9} $ $q = \dfrac{63p}{90} + \dfrac{40p}{90}$ $q = \dfrac{63p +40p}{90}$ $q = \dfrac{103p}{90}$